Refrigerated display case and elements thereof



Aug. 31, 1965 s. BECKWITH 3,203,337

REFRIGERATED DISPLAY CASE AND ELEMENTS THEREOF Filed Feb. 27, 1961 3Sheets-Sheet 1 F! G. 1 f

4m mu 5%: Fl 2 INVENTOIiQ.

Sterling Bcckwzih BYWM 7 Aug. 31, 1965 Filed Feb. 27, 1961 s. BECKWITH3,203,337

REFRIGERATED DISPLAY CASE AND ELEMENTS THEREOF 3 Sheets-Sheet 2 FIG, 42

IN V EN TOR.

" Sierlz'n Ecckwiz'fi Clii'ys United States Patent 3,203,337REFRIGERATED DISPLAY CASE AND ELEMENTS THEREOF Sterling lieckwith,Lihertyville Township, Lake County,

Ill., assignor, by mesne assignments, to Dual Jet Refrigeration(Tompany, a corporation of Illinois Filed Feb. 27, 1961, Ser. No. $1,8753 Claims. (Cl. 98-36) This invention relates to a method and means formaintaining a controlled atmosphere within a space having an open sideand it relates more particularly to a method and means for projection ofa gaseous curtain continuously across and open side of an otherwiseenclosed space for the purpose of maintaining a controlled atmospheretherein. The invention will hereinafter be described with reference tothe method and means for maintaining a refrigerated state within anopen-sided storage space. It will be understood that the same conceptscan be adapted to use for maintaining a warm, cold, inert, oxidizing,reducing, or the like atmosphere by proper substitution of elementsmaking up the gaseous curtain which is continuously projected across theopen side of the space.

In accordance with the practice of this invention, the desiredatmospheric condition is maintained within the open-sided space bycontinuously moving a panel of gaseous material across the open side ofthe space with the inner portion of the panel corresponding to theconditions desired to be maintained within the space while outerportions of the panel correspond more to the room conditions existingoutside of the space and it is a further concept of this invention toprovide a nozzle arangement and construction for use in combination withthe enclosed space to produce a panel formed of elements having a highdegree of laminar flow to produce a conditioning curtain which extendsacross the open space.

When used to produce a refrigerated space, the described panel is formedwith an inner portion containing refrigerated or cold air while outerportions contain warmer air. To produce a heated space, the conditionswould be reversed to provide the heated portion in the interior with thecolder portions outwardly thereof. Similarly, to produce an inertatmosphere, the inner portion of the panel will be formed of an inert orinertive gas while outer portions will be less inert, etc.

To the present, it has been common to manufacture cold storagecontainers for packaged foods, meats, beverages and the like in the formof an open top, rectangular container. The merchandise is displayed bypacking the items one upon the other. While keeping the contentssufiiciently cold to prevent spoilage, such display cases have thedisadvantage of being awkward from the standpoint of the. consumers usesince only the uppermost items in the stack are visible and it becomesnecessary to bend over to remove items from within such containers.

The present invention is adaptable to a new type of open side coldstorage container for displaying frozen goods. In such container, it ispossible for the various goods to be observed by the prospectivepurchaser and it is a simple matter to effect removal of the desirednumber of such goods without the necessity for bending or stooping tomake selections.

- In order to maintain a sufficiently cold atmosphere within theopen-sided container, a panel of substantially parallel layers of coldand warm air, for example, is projected across the open side of thecontainer. The inner portion of the panel which is adjacent the interiorof the container is formed with cold air having a temperature similar tothat of the interior. The outer portion of the panel has a temperaturemore closely approximating the temperature of the outside ambientatmosphere or a temperature intermediate therebetween.

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To function as a barrier to retain the cold within the container, boththe warm and cold air layers are projected at about correspondingvelocities, such for example as at St) to 1500 feet per minute, andpreferably 200 to 500 feet per minute, whereby entrainment is minimized.

To project the cold and warm air layers, hereinafter referred to as apanel, across the open side of the container, use is made of nozzlespositioned across one edge of the container with such nozzles beingarranged in side-byside parallel relation. For example, the nozzles mayextend across the bottom edge to direct the air streams towards the topedge, or the nozzles may be in the top edge to direct the streamsdownwardly towards the bottom edge, or they may be in one of the sideedges to direct the streams across towards the opposite side. The coldair nozzle is on the inside and is directed towards an inlet in theopposite edge for recirculation of the cold air and the warmer airnozzle, on the outer side, may be directed either into the ambientatmosphere or it too may be directed to an inlet for recirculation.

For a more complete description of the open-sided refrigerated storagespace, reference may be had to the Simons Patent No. 2,862,369, issuedDecember 2, 1958, and entitled Air Conditioned Display Compartment andMethod.

The concepts of this invention are addressed to an improvement tominimize turbulence and maximize laminar flow between the air streamsmaking up the air panel whereby intermixing of warm with cold air isminimized greatly to increase the etliciency of operation and maintenance of the desired atmospheric condition at minimum expense, and itis an object of this invention to provide a method and means forachieving same.

Another object is to provide a method and means for generating an aircurtain of the type described which is characterized by a high degree oflaminar flow substantially throughout the length and cross-sectionthereof.

A particularly important object of this invention is to provide laminarflow along the inner face between the moving streams of cold and warmair making up the air curtain or panel and it is a related object toprovide and improved nozzle arangement which functions to provide airpanels of the type described.

These and other objects and advantages of this invention willhereinafter appear and for purposes of illustration, but not oflimitation, an embodiment of the invention is shown in the accompanyingdrawings, in which:

FIG. 1 is a fragmentary top plan view of a nozzle assembly embodying thefeatures of this invention;

FIG. 2 is a cross-sectional view taken along the line 2-2 of FIG. 1;

FIG. 3 is a fragmentary top View of another modification of a nozzleassembly;

FIG. 4 is a sectional elevational view of the nozzle assembly of FIG. 3;

PEG. 5 is a sectional elevational view of a still further modificationof a nozzle construction;

FIG. 6 is a schematic illustration of the air flow from a nozzlearrangement of the type shown in FIG. 1;

FIG. 7 is a cross-sectional perspective view of an opensidedrefrigerated display case of the type with which the nozzles of thisinvention may be employed; and

FIG. 8 is an enlarged sectional view of a portion of the cabinet of FIG.7 showing in greater detail a nozzle construction which may be employedin the practice of this invention.

Before going into a detailed description of the nozzle asesmblies of theinvention, their mode of operation and the specific details of theirconstruction, consideration will first be given to a typical open-sidedrefrigerated dis play case of the type with which the nozzle assembliesare intended to be used. With reference to FIGS. 7 and 8,

the refrigerated display cabinet is constructed with a top wall 100,rear wall 102, bottom wall 103, and opposed end walls (not shown).Within the cabinet is an upper compartment 104, an intermediatecompartment 105 and a lower compartment 106. Within the uppercompartment there are provided refrigeration coils 107 and one or morecentrifugal blowers 108.

The middle or intermediate compartment 105 defines the area adapted tobe conditioned and within which the material 111 is positioned on abottom wall 109 with the exception that shelf 110 is preferably locatedon the bottom Wall for support of the material 111.

The bottom wall 109 extends to the end walls of the cabinet and to arear wall 112 which defines the rear wall of the intermediatecompartment 105. The rear wall 112, which is spaced inwardly from therear wall 102 of the cabinet, extends upwardly from the bottom wall 109to a position beyond the rear edge of the top wall 113 separating thecompartment 105 from the compartment 104-. The upper portion of wall 112is apertured for communication with the outlet of a blower 108 and isprovided with turning vanes 108 for directing the stream of air from theblower into the passage 114 defined by the wall 112 and the rear wall102 of the cabinet, which passage extends downwardly to the rear edge ofthe wall 109 of the compartment 105.

A plate 115 spaced below the bottom wall 100 of the compartment 105extends from the forward side of the compartment to the rear wall 102 ofthe cabinet. Thus plate 115 and bottom wall 109 form a continuation 116of the passage 114.

Below the refrigeration coils 107 and above the top wall 113, theassembly is provided with a plate 117 which extends rearwardly from thefront wall 131 of the upper compartment 104 to overlap a portion of thetop wall 113 of compartment 105 and in spaced relationship therefrom.Thus the wall 113 and plate 117 define a passage 118 therebetween whichis open to the forward side of the cabinet adjacent the upper side ofthe compartment 105 and which communicates with the upper compartment104 at a point forwardly of the Wall 112.

Air flow through the passage 118 and into the upper compartment 104passes across the refrigeration coils 107 before entering the inlet toblower 108. Thus the passages 114 and 116 represent the cold airpassages the walls of which define two of the walls of the compartment105 and thereby assist in conditioning air in compartment 105 to thedesired temperature.

Below plate 115 there is provided a spaced parallel wall 119 whichextends rearwardly from the forward lower side of the compartment todefine a passage 120 therebetween. The rear edge of plate 119 terminatesshort of the rear Wall 102 of the cabinet and then extends downwardly at121 to the bottom 103 of the cabinet. A blower 122 is positioned withinthe lower compartment 106 with its outlet in communication with thepassage 120 so that the air from the blower will be caused to flowthrough the passage 120. Inlet louvers 123 in the front Wall 124 of thecompartment 106 provide for the entry of atmospheric air to the inlet ofthe blower 122.

The walls defining the passages 116 and 120 are turned at their forwardedge to extend in an upwardly direction, as shown in FIG. 8, to providea pair of elongated upwardly directed nozzles 126 and 127 which extendin side-by-side relationship across the lower edge of the open front ofcompartment 105. The air forced through passages 116 and 120 issuesupwardly from the nozzles and across the front open side of thecompartment 105 in adjacent layers 128 and 129.

The inner layer 128 represents the refrigerated air issuing from thepassage 116 through the nozzle 126 while the outer layer 129 representsthe warmer air recirculated from the atmosphere from the passage 120through the nozzle 127. Above the pair of nozzles 126 and 127 and acrossthe upper edge of the compartment 104 is a depending lip 130 whichfunctions as a divider to separate the refrigerated layer 128 from thewarmer layer 129 whereby the air recirculated therough the refrigerationcoils and into passages 114 and 116 is air formed mostly of the cold airoriginally making up the cold air panel thereby to save on the cost ofrefrigeration and therefore also better to stabilize the coldtemperature conditions existing within the refrigerated space.

The inner and outer layers 128 and 129 issuing from the nozzles 126 and127 may be easily adjusted by controlling the output fans. Therefrigerated space is thus protected by a layer of air having atemperature substantially corresponding to the temperature at which itis ejected from nozzle 126, which may be at about 10 F to about -30 F.and which is therefore adequate to maintain a temperature ofapproximately 0 F. within the refrigerated space. Little, if any,entrainment occurs between the layers 128 and 129 which are moved insubstantially laminar flow at substantially the same velocity.

With the arrangement described, free access is had to the material 111through the open front side of the storage space. Where the materialsare in separate packages, they can be readily removed through the openfront in the same manner as any other package or article can be removedfrom conventional shelves. The labels are readable and the packages canbe arranged so that they will not interfere one with another.

The concepts of this invention are also adapted for use where the warmerair in the outer panel or panels is also separately recirculated asdescribed in the copending application of Hagen et al. Ser. No. 54,077,filed September 6, 1960, and entitled Refrigerated Display Case. In thearrangement of the Hagen et al. application, both the refrigeration orcold air jet and the warmer or guard air jet are projected for laminarflow across the open space from the nozzles extending across the topedge of the open space. The panels are directed downwardly against theopen space towards the correspondingly arranged inlets for separation ofthe cold air panel for recirculation through the refrigerated coils andpanels to the nozzles and jets, as previously desecribed, and forseparation of the warmer air panel for recirculation through passagesbetween the refrigeration passages and the outer walls of the cabinet tothe nozzles or jets from which the Warmer air is ejected across the openspace. The air in the guard jet will be warmer than the air in therefrigeration jet but colder than the ambient atmosphere so that theslight amount of guard air which intermixes with the refrigeration airduring passage together across the open space will have minimum effecton the horsepower of refrigeration required to maintain the desiredconditions Within the refrigerated space 105. Thus the desire forlaminar flow to minimize turbulence of intermixing of air from theadjacent air panels is present where the refrigeration air jet isrecirculated alone or in combination with one or more guard jets.

In accordance with the practices of this invention, it has been foundthat the turbulence may be substantially reduced by providing nozzles ofthe type illustrated in FIGS.1 and 2, but preferably arranged with aslight degree of convergence as between the inner cold air nozzle andthe outer warm air nozzle to avoid dead spots between panels and topromite laminar flow. These nozzles, for the most part, are adaptable toconstructions of the type shown in FIGS. 7 and 8.

The nozzle of FIG. 1 is designated generally by the numeral 10. Itconsists of a plurality of parallel, longitudinally spaced vanes ormembers 12 which subdivide the nozzle into a number of closelyseparated, parallel passages 14. The nozzle is shown in FIG. 2 as beinga continuation of the warm air duct 16 and the cold air duct 18 dividedby a wall 20. The outer wall of the warm air nozzle is designated by thenumeral 22 and the inner wall of the cold air nozzle by the numeral 24.It has been found that for minimum turbulence, it is desirable tomaintain minimum spacing between the jets issuing from the nozzles. Forthis purpose, it is desirable to minimize the cross-section of the vanesor walls between the open spaces from which the air jets issue.Satisfactory results are secured when the wall space comprises less thanone fourth of the cross-section of the nozzle or, in other words, whenthe nozzle is at least 75 percent open and less than 25 percent occupiedby vanes or walls 12. Best results are secured when the nozzle is 90preoent or more open and only percent or less wall or vanes. Typical ofa preferred construction is a honeycomb or vaned nozzle having a vane orwall thickness of 0.001 inch and a bore or open space between the wallsof about 0.125 inch.

A nozzle of the type described is designed so that the air columnsissuing from the air channels 16 and 18 comprise a plurality of fine airstreams which merge into adjacent panels of refrigerated and warm aircharacterized by substantially laminar or non-turbulent flow. In thepreferred practice of this invention, the nozzle sections comprise vanesections in the form of honeycomb or thin wall sections, such as formedof sheet aluminum. Best use is made of honeycomb slabs having a depthgreater than /2 inch and preferably greater than 1 to 2 inches so thatthe stream of air issuing from said honeycomb openings Will be guided inlaminar flow from the nozzles to provide for substantially laminar fiowacross the access opening in the front wall of the container. As ageneral rule, it may be stated that the passages between the dividingwalls should be such that the air emanating therefrom has a Reynoldsnumber below 2300 (based upon a channel having an equivalent diameterequal to one-half of the hydraulic radius), as corrected for the type ofchamber used in forming the cold and warm air panels. Since thedetermination of Reynolds numbers of critical velocities can best beachieved while in the steady state and while conversion from the steadystate characteristic of laminar flow to a transient state can includeturbulent flow, it is sometimes easier to make use of trial and error inconjunction with visual inspection, as by means of a smoke, to determineoptimum velocities of the air stream with a particular set of conditionsfor maximizing laminar flow.

In the smoke tests with the nozzle assembles of the type illustrated inFIGS. 1 and 2, it was noted that substantial laminar flow between theair panels occurred substantially throughout, with the possibleexception of the trailing edge of the panels where some degree ofturbulence Was noted in the inner face between the adjacent cold andwarm air panels. It was further noted that the extent of laminar flowincreased with an increase in the number of guard jets and decreased inproportion to the spaced relationship between the jets. Across anopening of about 24 inches, only a small fraction, corresponding to lessthan 20 to 30 percent and preferably less than 10 percent of the warmair panels, entered the colder air panels at the cutoff point where bothpanels were recirculated. A slightly greater degree of turbulence wasexperienced in upward flow of the air panels across the open space, asillustrated in FIGS. 7 and 8, as compared to down-flow from the top sideto the bottom side, as illustrated in the aforementioned copendingapplication. This difference is believed to be influenced somewhat bythe gravitational effect.

It has been found further that improvement in laminar flow or decreasein turbulence can be achieved by a slight modification in theconstruction of the nozzles of the type described and illustrated inFIGS. 1 and 2 to decrease the spaced relationship between the vanes 12in the outer portion of the outer nozzle and the inner portion of theinner nozzle, as illustrated in FIG. 3. The decrease in spacing can takeplace gradually from the inner edge towards the center and from theouter edge towdar the center, or it may be limited to only the outeredge portion of the outer nozzle and the inner portion of the innernozzle with the spacing throughout the remainder being somewhat thesame.

In another modification, illustrated in FIG. 4, the central portion orarea between both nozzles 46 and 48 is provided with a current of airfrom chambers 16 and 18. A small portion of the stream in chamber 16 iscut off by the wall 46 for passage between the walls 46 and 22 while asmall portion of the cold air stream in chamber 18 is cut off by wall 48for passage between the walls 48 and 24. These walls define passageways52 which are provided with vaned sections 50, such as honeycombsections, whereby velocity in the outer portion of the warm air streamand consequently turbulence in the inner portion of the cold air streamis reduced. The streams from the passages 16, 18 and 52 are finallyadvanced through the vaned sections of honeycomb 53 to define the airpanels projected across the open space.

A still further modification for subdivision of the air streams andregulating flow is shown in FIG. 5 wherein the air streams are turned atsharp angles for issuance from the nozzles and 62 by vaned or honeycombsections 64 and 66, which are formed to curvilinear shape at theirleading edges to intercept variable amounts of the air streams passingthrough the chambers. This procedure is adapted to increase or decreasethe volume of air issuing from selected cross-sections of the nozzles.In the modification illustrated in FIG. 5, the curvilinear contour atthe intercepting leading edge portions of the turning vanes is such thatsmaller amounts of the air stream are intercepted at the inner edgeportion of the cold air stream and at the outer edge portion of thewarmer air stream so that a less volume of the stream issues from theinner edge portion of the cold air nozzle and the outer edge portion ofthe warm air nozzle with maximum volume from the remainder. For thispurpose, the turning vanes are curved to extend across the path of theair stream with a flattened portion 68 of the curve in the inner edgeportion of the section 64 with the steepest portion of the curve at theouter edge portion of said nozzle section. Similarly, the honeycomb inthe nozzle 62 is formed with the steepest portion of its curve at theinner edge with the flatten portion at the outer edge so that minimumvolume of the air streams in the feeding channels will be cut off forpassage through the vanes having the more flattened curvature.

As previously mentioned, an expedient method for arrangement of thenozzle assemblies embodying the features of this invention is tointroduce a smoke for visual reproduction of the characteristics of theair curtain issuing from the particular nozzle arrangement. FIG. 6illustrates the type of air curtains produced by a nozzle assembly ofthe type shown in FIG. 1. The striated smoke panel 57 emanating from thenozzle possesses characteristics of laminar flow in the central portionof the nozzle at the inner face between the air panels for a distancegreater than the portions 54 and 55 adjacent the outer edges of thepanel. When the smoke reaches a substantial height above the nozzlearea, turbulence begins to be experienced at the inner face between thepanels, as shown in the figure at 56. At the inner face between thepanels, characteristics of the air flow are maintained for a substantialdistance, as shown by the numeral 58.

Since pressure differences exist as between the interior of the enclosedspace and the exterior or ambient atmosphere and since such pressuredifferences may vary over a period of time and from one edge to theother across the open space, it is desirable to embody means to positionthe nozzles at an angle so that the resultant merged jet issuing fromthe nozzle is so directed that the inertia forces deflecting the jetfrom a straight line oppose any differences in pressure across theopening. It is desirable also to angle the jet to oppose uniformpressure differences along the length of the jet. It is also desirableto embody. means for adjusting the angle of the jets to oppose variablepressure differences across the width of the jet and to vary the angleor aim to compensate for variations in pressure with time. Fornon-varying conditions, the angle of the jets can be fixed to provide aresultant stream which bends in response to pressure differences acrossthe opening to bring the trailing edge of the stream to the inlets forproper cutoff and recirculation. For transient conditions, the angle oraim of the jets should also be transient or variable to oppose variationin pressure. Such adjustment can be made respon sive to pressurediiferences existing across the opening.

It will be apparent from the foregoing that I have provided a simple andexpedient means for maintaining laminar flow between adjacent panels ofair making up an air curtain projected across a conditioned spacewhereby the desired conditions can be maintained within said space witha minimum expenditure of conditioning material, cold, heat or otheratmospheric control means.

It will be understood that changes may be made in the details ofconstruction, arrangement and operation Without departing from thespirit of the invention, especially as defined in the following claims.

I claim:

1. A nozzle assembly for use in maintaining nonentraining parallelpanels of diiferently conditioned air across the open side of anotherwise enclosed space which comprises at least two nozzles arrangedin side by-side relationship to extend continuously along the length ofone edge of the open side and positioned to direct the air panelstowards the opposite edge thereof, one of said nozzles being an innerconditioned air directing nozzle having an inner edge portion positionedadjacent the open side of the enclosed space, the other nozzle being anouter differently conditioned air nozzle having an outer edge positionedtowards the ambient atmosphere, said nozzles embodying means for issuingthe air streams at lower velocity from the inner portion of the innernozzle and from the outer portion of the outer nozzle than the airstreams issuing from other portions of the inner and outer nozzles, saidmeans comprising a plurality of vanes extending lengthwise across eachof the nozzles dividing the nozzles into vaned sections, and additionalvaned sections in communication with the vaned sections in the innerportions of the inner nozzle and the outer portions of the outer nozzleto impart resistance to gaseous flow whereby the volume of air passingthrough said vaned sections having barriers is less than through theremainder of the vaned sections with corresponding decrease in velocityof air issuing from the corresponding inner portions of the inner nozzleand outer portions of the outer nozzle.

2. A nozzle assembly for use in maintaining nonentraining parallelpanels of cold and warm air across the open side of a cold storagecontainer which comprises at least two nozzles in side-by-siderelationship and extending continuously across the length of one edge ofsaid open side for directing the air panels towards the opposite edgethereof, one nozzle being a cold air directing nozzle having its inneredge positioned adjacent to the open side of the cold storage container,the other nozzle being a warmer air directing nozzle having an outeredge positioned towards the ambient atmosphere, comprising an inner airpassageway communicating with the inner nozzle and an outer airpassageway communicating with the outer nozzle, walls spaced from theouter walls of the two passageways and projecting into the passagewayssubdividing the passageways into inner and outer passages incommunication with the nozzles, flow restriction means within the innerpassage of the inner air passageway and within the outer passage of theouter air passageway for slowing air flow whereby the air issues fromthe nozzles at a lower velocity from the inner portion of the innernozzle and from the outer portion of the outer nozzle by comparison withthe remainder.

3. A nozzle assembly for use in maintaining nonentraining parallelpanels of diiferently conditioned air across the open side of anotherwise enclosed space which comprises at least two nozzlesarranged inside by side parallel relationship to extend continuously along thelength of one edge of the open side and positioned to direct the airpanels towards the opposite edge thereof, one of said nozzles being aninner conditioned air directing nozzle having an inner edge portionpositioned adjacent the open side of the enclosed space, the othernozzle being an outer differently conditioned air nozzle having an outeredge positioned towards the ambient atmosphere, said nozzles embodyingmeans for issuing air streams at lower velocity from the inner portionof the inner nozzle and from the outer portion of the outer nozzle thanfrom the air streams from the outer portion of the inner nozzle and theinner portion of the outer nozzle, said means comprising a plurality ofvanes extending lengthwise across each of the nozzles in substantiallyequally spaced apart relationship to subdivide each nozzle into aplurality of vaned sections of substantially equal cross section, airpassageways leading into each of said nozzles from a directionsubstantially perpendicular to said nozzles, said vanes terminating attheir rearward ends in said passageways with each adjacent vaneprogressively extending inwardly by increasing amounts from the innerend outwardly in the inner nozzle and from the outer end inwardly fromthe outer nozzle whereby the increments of air cut off for passage intoeach of the vaned sections increases from the inner end outwardly in theinner nozzle and from the outer end inwardly in the outer nozzle withcorresponding difference in the velocity of air issuing from the vanedsections of the nozzles.

References Cited by the Examiner UNITED STATES PATENTS 1,971,173 8/34Bennett et al. 9838 2,467,505 4/49 Sidell 9836 2,855,760 10/58 Simons9836 X 2,855,762 10/58 Zehnder 9836 X 2,862,369 12/53 Simons 98-36 X2,863,373 12/58 Steiner 9836 2,935,925 5/60 DOoge 9836 2,976,794 3/61Allander et al. 98-38 3,010,379 11/61 Arzberger 9836 3,021,776 2/62Kennedy 9836 FOREIGN PATENTS 518,391 3/53 Belgium.

ROBERT A. OLEARY, Primary Examiner.

CHARLES E. OCONNELL, Examiner.

1. A NOZZLE ASSEMBLY FOR USE IN MAINTAINING NONENTRAINING PARALLELPANELS OF DIFFERENTLY CONDITIONED AIR ACROSS THE OPEN SIDE OF ANOTHERWISE ENCLOSED SPACE WHICH COMPRISES AT LEAST TWO NOZZLES ARRANGEDIN SIDE-BY-SIDE RELATION SHIP TO EXTEND CONTINUOUSLY ALOGN THE LENGTH OFONE EDGE OF THE OPEN SIDE AND POSITIONED TO DIRECT THE AIR PANELSTOWARDS THE OPPOSITED EDGE THEREOF, ONE OF SAID NOZZLES BEING AN INNERCONDITIONED AIR DIRECTING NOZZLE HAVING AN INNER EDGE PORTION POSITIONEDADJACENT THE OPEN SIDE OF THE ENCLOSED SPACE, THE OTHER NOZZLE BEING ANOUTER DIFFERENTLY CONDITIONED AIR NOZZLE HAVING AN OUTER EDGE POSITIONEDTOWARDS THE AMBIENT ATMOSPHERE, SAID NOZZLES EMBODYING MEANS FOR ISSUINGTHE AIR STREAMS AT LOWER VELOCITY FROM THE INNER PORTION OF THE INNERNOZZLE AND FROM THE OUTER PORTION OF THE OUTER NOZZLE THAN THE AIRSTREAMS ISSUIGN FROM OTHER PORTIOSN OF THE INNER AND OUTER NOZZLES, SAIDMEANS COMPRISING A PLURALITY OF VANES EXTENDING LENGTHWISE ACROSS EACHOF THE NOZZLES DIVIDING THE NOZZLES INTO VANED SECTIONS, AND ADDITIONALVANED SECTIONS IN COMMUNICATION WITH THE VANED SECTIONS IN THE INNERPORTIONS OF THE INNER NOZZLE AND THE OUTER PORTIONS OF THE OUTER NOZZLETO IMPART RESISTANCE TO GASEOUS FLOW WHEREBY THE VOLUME OF AIR PASSIGNTHROUGH SAID VANED SECTIONS HAVING BARRIERS IS LESS THAN THROUGHT THEREMAINDER OF THE VANED SECTIONS WITH CORRESPONDING DECREASE IN VELOCITYOF AIR ISSUING FROM THE CORRESPONDING INNER PORTIONS OF THE INNER NOZZLEAND OUTER PORTIONS OF THE OUTER NOZZLE.